Fresh and stored coals from the United States (New Mexico, Colorado and Wyoming) and Czech Republic (North Bohemian and Upper Silesian Basins) were studied by the method of temperature programmed desorption. Desorbed gases were analyzed for their chemical and carbon isotope composition. Upon heating from room temperature with a constant rate of 40 degrees C/min, two desorption phases were observed: low temperature desorption of CH(4) and CO(2) with a maximum intensity between 50 and 80 degrees C and high temperature desorption of CO(2) only between 150 and 210 degrees C. The desorption of (residual) primary coalbed gas was compared with the desorption of re-adsorbed gases. The delta(13)C values of the desorbed gases changed due to isotopic fractionation during coal degassing. Kinetic isotope effects were evaluated by comparing the gas desorption from fresh and stored coals from the same seams. Mean values of isotope enrichment during desorption are 2 parts per thousand and 1.9 parts per thousand for CO(2) and CH(4), respectively. (C) 2009 Elsevier Ltd. All rights reserved.